polyphase

Syntax

Description

p = polyphase(sysobj)
returns the polyphase matrix p of the multirate filter
System
object™
sysobj. Each row in the matrix corresponds to a polyhase
branch. The number of columns in p corresponds to the number of
filter taps per polyphase branch.

p = polyphase(sysobj,'Arithmetic',arithType)
returns the polyphase matrix p in the precision set by the
arithType.

Examples

Polyphase Matrix of an FIR Interpolator

When you create a multirate filter that uses polyphase decomposition, polyphase lets you analyze the component filters individually by returning the components as rows in a matrix. First, create an interpolate-by-three filter.

arithType — Arithmetic type'double' (default) | 'single' | 'Fixed'

Specify the arithmetic used in computing the polyphase matrix. When you
specify 'double' or 'single', the
function performs double- or single-precision analysis. When you specify
'fixed' , the arithmetic changes depending on the
setting of the CoefficientDataType property and whether
the System
object is locked or unlocked.

Details for Fixed-Point Arithmetic

System Object State

Coefficient Data Type

Rule

Unlocked

'Same as input'

The function assumes that the coefficient data type is
signed, 16 bit, and autoscaled. The function performs
fixed-point analysis based on this assumption.

Unlocked

'Custom'

The function performs fixed-point analysis based on the
setting of the
CustomCoefficientsDataType
property.

Locked

'Same as input'

When the input data type is 'double'
or 'fixed', the function assumes that the
coefficient data type is signed, 16-bit, and autoscaled. The
function performs fixed-point analysis based on this
assumption.

Locked

'Custom'

The function performs fixed-point analysis based on the
setting of the
CustomCoefficientsDataType
property.

When you do not specify the arithmetic for non-CIC structures, the
function uses double-precision arithmetic if the filter System
object is in an unlocked state. If the System
object is locked, the function performs analysis based on the locked
input data type. CIC structures only support fixed-point arithmetic.

Output Arguments

p — polyphase matrixmatrix

Polyphase matrix p of the multirate filter. Each row in
the matrix corresponds to a polyhase branch. The first row of matrix
p represents the first polyphase branch, the second
row the second polyphase branch, and so on to the last polyphase branch. The
number of columns in p corresponds to the number of
filter taps per polyphase branch.